Yes you can host multiple domain names on one account, and use other techniques to setup different websites for each address.
The approach to hosting multiple websites might depend on which platform you use, but typically they tweak the .htaccess file to redirect to a subdirectory per website.
Although we place no limits on this approach, we don't advise nor provide personal support for this. If you host multiple websites on one website space, you are only going to slow down your website speed, as each website fights for resources.
In comparison, when each website has it's own web space, each website is guaranteed more RAM and CPU each. Each website will end up hosting at a speed equivalent to the best possible speeds.